In the field of wireless cellular systems, which are represented by, for example, mobile phones, service modes become diverse, and transmitting large capacity data such as still images and movies in addition to voice data is in demand in recent years.
IMT-2000 cellular system is already in service, and, meanwhile, 3GPP LTE (3GPP Long Term Evolution), which requires a peak rate of 100 Mbps in downlink, is underway to standardize. Then, as a category to aim at further advancement, the standardization of IMT-Advanced is about to start. This IMT-Advanced provides requirement parameters where a rate of several Gps, 100 MHz bandwidth in downlink and a rate of hundreds of Mbps with 40 MHz bandwidth in uplink, that is, this IMT-advanced requires greatly exceeded breakthrough than IMT-2000.
In particular, to use radio resources effectively under situations where uplink and downlink both become wide bands, frequency resource allocation or link adaptation according to frequency response (i.e. the quality per frequency subdivided inside the bands and CQI (Channel Quality Indicator)) is essential. However, in a case of FDD (Frequency Division Duplex) using different frequencies between uplink and downlink, frequency response is different between the uplink band and the downlink band, so that a radio base station apparatus (Node B) and a mobile terminal apparatus (UE) need to transmit, for example, pilot signals to measure the frequency response of each band.
Usually, a pilot signal is necessary for synchronous detection upon data transmission, and the pilot signal for that reason may be transmitted in the band alone where data is transmitted. However, a pilot signal for quality measurement, which is required in frequency resource allocation, needs to be transmitted in the entire band or in a wider band than the data to be transmitted, and furthermore needs to be transmitted whether or not there is data.
Naturally, to measure accurate frequency response, a pilot signal and so on may be transmitted in the entire band, and, if a mobile terminal apparatus transmits a pilot signal in the entire uplink band, there is a drawback of accelerating the battery consumption. Further, when a UE located at a cell boundary transmits a pilot signal in the entire band and great power, interference on surrounding cells increases and uplink throughput of the overall system decreases.
Further, if a pilot signal for CQI measurement is transmitted in a wide band when transmission power is limited to reduce battery consumption, the received power density in the radio base station apparatus decreases, and therefore CQI measurement error increases. Particularly, this affects the UE near a cell boundary remarkably. If the CQIs with measurement error increase is responded, frequency band allocation cannot be carried out properly, and therefore overall uplink throughput in a cell decreases.
The method of reducing power consumption of the mobile terminal apparatuses includes a method of decimating transmission of a pilot signal for CQI measurement in the time domain and the frequency domain. One example is disclosed in Non-patent Document 1. With this method, the bandwidth for transmitting a pilot signal for CQI measurement is controlled according to path loss. To be more specific, the UE that is near the base station apparatus and that has small path loss transmits a pilot signal for CQI measurement in a wide bandwidth, and the UE that is near a cell boundary and that has large path loss transmits a pilot signal for CQI measurement in a narrow bandwidth.    Non-patent Document 1: “Frequency Domain Channel-Dependent Scheduling with Group-wised Allocation of Transmission Bandwidth of Pilot Channel for CQI Measurement in Single-Carrier FDMA-Based Evolved UTRA Uplink” Technical Report of IEICE, RCS2006-154, October, 2006, Ofuji, Kawamura, Higuchi and Sawahashi